Venus and Jupiter dance in the night sky

Look to the skies in the coming days to see Venus and Jupiter close in on each other.

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If skies are clear, look to the northwest at twilight for the next few days to see the two brightest planets apparently moving close together.

Of course, Venus and Jupiter are vast distances apart, but they look like they are closing in on each other in what is known as a conjunction. The apparent proximity occurs because all the planets in the solar system travel on roughly the same plane.

According to the Royal Astronomical Society of New Zealand (RASNZ), Venus and Jupiter will appear closest tomorrow.

They have already appeared quite close for several evenings and will continue to do so for several more after tomorrow.

Look for them soon after sunset. Both would be easily visible 15 minutes later, RASNZ said.

"Don't leave it too late, the planets soon get very low and set about 90 minutes after the Sun."

RASNZ publicity officer Haritina Mogosanu said the two planets were easy to find.

"Jupiter and Venus are the brightest. That's what makes it so spectacular," she said.

Conjunctions are not rare events, with Venus and Jupiter doing it again in 14 months.

But Northern Hemisphere inhabitants are rather excited about the current version, which for them will be the best for years to come. At mid-northern latitudes the two planets will be out for nearly four hours after sunset.

For Venus, this month's conjunction is not the only reason it will be attracting attention in 2012.

June 6 is the date for one of the famed transits of Venus, when the planet passes in front of the sun. It is the same phenomenon that led James Cook to leave England in 1768 bound for Tahiti, the same voyage in which he reached New Zealand for the first time.

Transits of Venus happen in pairs eight years apart, followed by a large gap. It happened in 2004, and will not reoccur until 2117.

The aim of Cook's hazardous journey was to take part in efforts to work out the size of the solar system.

Recording the start and stop times of the transit from widely spaced places on earth would theoretically enable that to happen. Unfortunately, the technology at the time of the June 1769 transit was not good enough, and it was not until the next pair of transits in the 19th century that the problem was solved.

RASNZ said no one alive had seen a transit of Venus from this country, with the 2004 event having been visible from the other side of the Earth.

As seen in New Zealand, the 2012 transit would last for nearly 6-1/2 hours, visible as an intensely black dot making its way across the face of the Sun. All stages of the transit would be visible from New Zealand, although the Sun would be very low for the final part, just before Venus moved off.